Martensitic transformation and magnetism in Ni and Fe-rich compositions of Ni-Fe-Ga shape memory alloys

First principles spin polarized calculations have been performed to study the martensitic transformation and magnetism in stoichiometric and off-stoichiometric compositions of Ni-Fe-Ga shape memory alloys. The energy difference between cubic phase and non-modulated tetragonal phase has been estimated. The calculated shear elastic constants are found to have correlations with the valence electron concentration per atom (e/a value). From the analyses on local magnetic moments, it is observed that direct and indirect magnetic exchange occur in these alloys. The Curie temperatures estimated from the exchange parameters are found to be sensitive to the change in alloy composition.